The decision means that up to 267 asylum seekers on the mainland could be sent back to the island nation, where a large number of serious sexual assaults have been reported. A Senate inquiry also raised serious concerns about conditions on Nauru, where infant children are being held.

But 10 Anglican and Uniting churches around the country have offered sanctuary to the asylum seekers who are at risk of being returned.

The right to sanctuary, while not now recognised under common law in Australia or other jurisdictions, is a biblical concept that had legal basis during the middle ages.

The Anglican Dean of Brisbane, the Very Reverend Dr Peter Catt, said he was prepared to be charged with an offence for obstruction by trying to prevent federal authorities from entering the cathedral grounds.

“We offer this refuge because there is irrefutable evidence from health and legal experts that the circumstances asylum seekers, especially children, would face if sent back to Nauru are tantamount to state-sanctioned abuse,” he told ABC Radio National on Thursday.

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There is an offence under Australian law for “concealing and harbouring non-citizens”, which could potentially be used against the heads of churches seeking to prevent asylum seekers from being deported.

The federal government has continued to stress its support for offshore detention. The prime minister, Malcolm Turnbull, said on Wednesday he had a “steadfast” resolve to prevent people smugglers.

Immigration minister Peter Dutton said the government would not be “dragging people out of churches” but insisted that the people’s cases would be individually considered on medical advice.

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Dutton said the bulk of the group were people who were accompanying ill family members. Once medical assistance was completed the government would be looking to send people back to Nauru or to their country of origin with financial assistance.

Dutton reiterated his intention not to put any child in harm’s way. “We have to be compassionate on one hand but we have to be realistic about the threat from people smugglers. We’re acting in the best interests not only for these children but children that would follow them.”